Many of the agricultural workers in central asia’s cotton fields are
a. slaves
b. children
c. servants
d. soldiers

A. I may be wrong but back in history there was a lot of slavery going on through routes like Asia

C. naturally in the environment

Geothermic gradient is the rate of increasing temperature with respect to increasing the depth in the earths interior. away from tech tonic plates boundaries, it is about 25-40 c/km (72-87 degrees f/mi) of depth near the surface in most of the world.